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  <script>

    // for循环的嵌套: 循环中执行体, 里面又嵌套了循环
    for (var i = 0; i < 10; i++) {

      console.log("i开始执行:", i)

      for (var j = 0; j < 3; j++) {
        console.log("执行j循环")
      }

      console.log("i结束执行:", i)
    }

  </script>

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